Technical Abstract:
Excessive nutrients in surface runoff, especially from manure applications, has been a well-recognized environmental concern. Research in this subject area has been focused on relating surface runoff and soil erosion to nutrient loading with little consideration of physico-chemical conditions of the soil that may affect the chemical transport. In this research, we hypothesized that prolonged saturation may cause a change in soil surface condition, and subsequently, affect runoff and sediment production. A rainfall simulation experiment was conducted on soil pans to examine the effects of liquid swine manure application on runoff and soil loss under different hydrologic conditions. Results showed a significant change in soil loss due to manure application after 1, 7 and 28 days moisture equilibration. A possible explanation for the change in erosion is that the changes in chemical state of the moist soil and their interaction with ions in the manure, especially Na and K, affected soil aggregation and consequently, soil dispersion and loss.